The present invention is related to an ultrasound therapy system for irradiating focused ultrasound used in medical treatments, and more specifically, is directed to such an ultrasound therapy system equipped with an intraluminal catheter functioning as a supplementary role of medical treatments.
Various therapeutical methods are known in the field so s to execute minimally invasive tissue treatments by irradiating ultrasound from an outside of a body, or in an intraluminal manner. For instance, there is such a therapeutical method for a prostate by employing an ultrasound generator which is arranged inside a rectum.
As an example of ultrasonic therapy applicable to a disease related to a prostate, a prostatomegaly may be cited. A prostatomegaly implies such a disease that since at least a portion of a prostate becomes a hypertrophy, a urethra is bent, so that a patient must conspicuously have an obstruction of a urinary stream, an urgency of voiding, and a frequent urination. As therapeutical methods, the following methods have been proposed, namely, a method for removing a disease portion by a surgical operation, and a method for burning out a disease portion by irradiating a laser thereto. In contrast with these methods, when the ultrasound therapy apparatus disclosed in U.S. Pat. No. 5,676,692 is employed, medical operations can be carried out in a simpler manner, and also an early recovery from the medical operation could be expected. This ultrasound therapy apparatus is arranged by the therapeutical probe, the ultrasonic diagnostic apparatus connected to the therapeutical probe, the power supply used to generate the focused ultrasound, and also the urethral catheter for reflecting the ultrasound. This therapeutical probe contains the focused ultrasound generating source having the two roles, namely, the generation of the continuous wave for therapeutical purposes, and also the generation of the pulse wave used to acquire the ultrasound tomographic image. As the therapeutical method, under such a condition that the catheter is firstly inserted from a urethra to a bladder, the ultrasonic tomographic apparatus probe is inserted into a rectum so as to acquire an ultrasonic tomographic image of a region in the vicinity of the urethra. Thus, a target region for medical treatment is previously determined. Next, the therapeutical probe is inserted into the rectum, and the ultrasonic tomographic image of the region in the vicinity of the prostate is acquired from the ultrasonic pulse signal derived from the therapeutical probe. In this ultrasound therapy apparatus, the ultrasound-generating source for ultrasonic tomographic images may have another function of the therapeutical ultrasound generating source capable of irradiating the continuous wave, it is practically difficult to optimize this ultrasound generating source in order to generate such a pulse wave used to produce the diagnostic tomographic image. That is, it is practically difficult to obtain tomographic images having better image qualities. As a consequence, in this therapy apparatus, while the catheter having the function capable of reflecting the ultrasound is employed, this apparatus is arranged in such a manner that the reflection signals having the strong strengths can be obtained from the catheter. Since the position of the catheter within the tomographic image is confirmed, such a confirmation is made of the position of the target region for treatment within the tomographic image obtained by employing this therapy apparatus. This treatment target region is indicated in such a tomographic image which has been previously acquired by using the ultrasonic tomographic apparatus probe. After the above-described operations have been carried out, the ultrasound for therapeutical purposes is irradiated from the therapeutical probe to the treatment target region. Normally, a time duration required for irradiating ultrasound one time is approximated to several seconds. In the case that a plurality of target regions are medically treated, normally, intervals of approximately 15 seconds are induced. The therapeutical effects may be conceived by the following reason. That is, since the ultrasound is irradiated onto a tissue, this tissue is heated at such a temperature higher than, or equal to the temperature at which this tissue is brought into the thermo-coagulation.
On the other hand, in the case that ultrasound is irradiated onto a living body, it is known that such a cavitation phenomenon may occur other than the heating effect. In this cavitation phenomenon, bubbles called as xe2x80x9ccavitationxe2x80x9d are produced and will collasp after being grown. Since both the chemical effect and the mechanical effect can be obtained by this cavitation phenomenon, also in the therapeutical operation using the ultrasound, therapeutical effects may be achieved by actively producing the cavitation and by solely utilizing the chemical effect and/or the mechanical effect achieved by this cavitation, or by combining these chemical/mechanical effects with the heating effect by the ultrasound. In such a case that ultrasound is irradiated from an inrectum portion toward a prostate and the like, this ultrasound may constitute a progressive wave condition. However, usually, cavitation can be hardly produced under such a progressive wave condition. To easily produce such a cavitation, the following fact is known. That is, while a substance and the like, which may reflect ultrasound, are employed, the ultrasound is advantageously irradiated under a standing wave condition. In the therapeutical method described in the above-explained U.S. Pat. No. 5,676,692, the reason why the catheter having the feature of reflecting the ultrasound is employed is intended to this cavitation effect. In other words, on the side of the ultrasound generating source for therapeutical purposes from the catheter, the ultrasound directly reached from the ultrasound generating source for therapeutical purposes is overlapped with the reflection wave from the catheter, so that the temperature increase can be effectively achieved. In addition thereto, since the progressive wave produced from the ultrasound generating source for therapeutical purposes and the reflection wave from the catheter may produce the standing wave, the cavitation effect can be promoted.
As previously disclosed in U.S. Pat. No. 5,523,058, with respect to this cavitation technique, the following fact is known. That is, since one frequency component is superimposed on a doubled frequency component, such ultrasound having a waveform suitable for this cavitation may be obtained even under the progressive wave condition.
Roughly speaking, there are three problems in the conventional therapeutical methods for the prostatomegaly with employment of the focused ultrasound.
As a first problem, the conditions of the prostate cannot be confirmed during medical treatments. In the case that the prostate is brought into the prostatomegaly state, even if the prostatomegaly portion is cut out, since this cut prostate will normally recur after a predetermined time period has passed, such a medical treatment must be carried out many times. To extend a treatment interval, it is desirable to remove such a prostatomegaly portion having a permittably wide area within a single medical treatment. On the other hand, in order to improve a quality of life after medical operation, it is desirable to avoid such irradiation of ultrasound onto a sphincter:muscle and an outlet of seminal vesicle. In the conventional therapy apparatus, since the energy of the focused ultrasound for therapeutic purposes is considerably larger than the energy of the ultrasound used to acquire the diagnostic image, the tissue tomographic image could not be acquired while the therapeutical ultrasound is irradiated, because of the reflection waves and the scattering waves caused by the therapeutical ultrasound. As a result, while the conventional therapy apparatus is employed, the suddenly-occurring positional shifts during herapeutical ultrasound irradiation cannot be properly corrected. In such a case that the medical treatment capable of achieving the high quality of life after the medical operation is wanted to be realized, the ultrasound could be irradiated only to such a narrow region, while excluding not only the region to which the ultrasound should be avoidably irradiated, but also an area located within a predetermined range (for example, 2 cm) from this irradiation avoidable region. As previously explained, in the conventional therapy apparatus, since the conditions of the prostate cannot be confirmed during the medical treatment, the following problem arises. That is, it is practically difficult to realize at the same time both achieving of the quality of life, and excising of the prostate over the wide range.
As a second problem, the energy owned by the focused ultrasound could not be concentrated to the treatment region in a high efficiency. In the conventional technique, the standing wave is produced based upon the reflection waves reflected from the urethral catheter. However, since the reflection waves are used, the amplitudes and the radiation directions of these reflection waves could not be controlled. Therefore, it is expected to promote the cavitation, which is not caused by the reflection waves from the catheter.
As a third problem, both the treatment region and the treatment range can be hardly controlled.
In general, a strength of ultrasound used in a medical treatment is wanted to be such a large value by which a temperature of a tissue can be increased higher than, or equal to a thermocoagulation temperature of this tissue for several seconds. Strengths of ultrasound which are sufficiently required so as to coagulate protein will differ from each other, depending upon conditions. In the conventional therapy apparatus, since it is normally difficult to confirm the coagulation of the tissue by checking a change contained in the ultrasound image, such ultrasound having sufficiently large strengths must be used. However, as explained above, if the medical treatment is carried out while the strength of the ultrasound is fixed to such a value which has been determined before the medical operation, then the strengths of the ultrasound may become excessively large, depending upon a certain condition. As a result, boiling happens to occur near a focal point of the ultrasound, and therefore, bubbles may be produced. When such bubbles are produced, energy of the ultrasound is reflected toward the transducer that generated the focused ultrasound. As a consequence, such a region whose ultrasound intensity is high will occur in front of this focal point. A boiling phenomenon may occur in such a region whose ultrasound intensity is high, and which is located in front of the focal point, and thus, bubbles are produced. Furthermore, another region whose ultrasound intensity becomes high may occur in front of the focal point. As a consequence, if the boiling phenomenon occurs in the vicinity of the focal point, then such a region whose ultrasound intensity is high may successively appear in front of the focal point. When this phenomenon occurs, the coagulation caused by the ultrasound may occur in an avalanche manner, so that the coagulated region is gradually extended toward the transducer that generated the focused ultrasound. In the worst case, the regions up to the rectum wall would be thermally denatured. The conventional therapy apparatus could not properly avoid such an avalanche extension of the coagulated region which is caused by productions of such bubbles.
As a consequence, an object of the present invention is to provide such an ultrasound therapy apparatus (system) capable of confirming an irradiation region of focused ultrasound in high precision, and thus capable of readily increasing an efficiency of a medical treatment.
Another object of the present invention is to provide an ultrasound therapy apparatus (system) capable of readily controlling a generation of cavitation.
A further object of the present invention is to provide an ultrasound therapy apparatus (system) capable of previously avoiding such an event that unnecessary and harmful thermo-denaturation would be conducted into any region other than a target region, which is caused by excessively irradiating ultrasound, and by extending a boiling area due to generations of bubbles.
An ultrasound therapy apparatus, according to an aspect of the present invention, is featured by such an ultrasound therapy apparatus comprising: a first ultrasound transducer for generating focused ultrasound used in therapeutical purposes; an ultrasound probe arranged in such a manner that the ultrasound probe is moved in combination with the first ultrasound transducer; an intraluminal catheter used to be inserted into a region in the vicinity of an irradiation target region of the focused ultrasound; and imaging means for forming an ultrasound tomographic image in such a manner that while imaging ultrasound is repeatedly transmitted from the ultrasound probe, reflection wave responses are acquired by sequentially scanning reception signals of reflection signals thereof along a lateral direction; wherein: the intraluminal catheter is comprised of: a second ultrasound transducer; and drive means for driving the second ultrasound transducer to generate ultrasound during an imaging operation by the ultrasound imaging means; and also the imaging means superimposes a sound source image which is caused by the ultrasound produced by the second ultrasound transducer on the ultrasound tomographic image.
Even while the focused ultrasound is irradiated, the above-explained sound source image clearly indicates the position of the second ultrasound transducer (position of imaging means, namely relative position of this imaging means with respect to focused ultrasound for therapeutical purpose). In the case that after the position of the second ultrasound transducer has been previously set to a region in the vicinity of the target region for ultrasound irradiation by positioning the catheter at a certain depth within the body cavity, the imaging operation is carried out, it is possible to monitor as to whether or not the focused ultrasound is correctly irradiated onto the target region with reference to the above-described sound source image. Even while the focused ultrasound is irradiated, it is possible to monitor as to whether or not the focused ultrasound is correctly irradiated onto the target region.
When the above-described second ultrasound transducer is driven by the continuous wave, the above-described sound source image becomes a line-shaped image, and thus, indicates only azimuth where the second ultrasound transducer is located. In this case, assuming now that the drive means may drive the second ultrasound transducer in a pulse-shaped mode, the ultrasound therapy apparatus is further comprised of a setting means for setting that the drive timing of the second ultrasound transducer is adjustable with respect to the repetitive ultrasound transmission by the imaging means. As a result, the above-explained sound source image becomes such a point-shaped image which may have information as to not only the azimuth direction, but also the depth direction of the ultrasound transducer. Under such a condition that the above-explained setting means is previously adjusted in such a way that the image of the second ultrasound transducer produced by the reflection waves is overlapped with the above-explained sound source image produced by the pulse-wave driving operation while observing the ultrasound tomographic image, and thereafter, both the pulse-wave driving operation of the transducer and the imaging operation of the tomographic image are repeatedly carried out while keeping this setting condition, the above-explained sound source image can continuously indicate the position of the second ultrasound transducer in the correct manner.
Instead of the above-explained arrangement equipped with the setting means for setting the manual timing, another drive means may be arranged. This drive means drives the second ultrasound transducer immediately after the drive means detects that the imaging ultrasound is reached to the second ultrasound transducer. In any of these arrangements, since the sound source image may appear on the ultrasound tomographic image and this sound source image is produced not only by the reflection wave response, but also the pulse-shaped ultrasound transmitted from the second ultrasound transducer itself, the position of the inserted second transducer can be clearly indicated even when the tomographic image is slightly disturbed by irradiating the focused ultrasound for therapeutical purposes. Eventually, it is possible to monitor as to whether or not the focused ultrasound for therapeutical purposes can be irradiated onto the correct position.
Also, an ultrasound therapy apparatus, according to another aspect of the present invention, is featured by such an ultrasound therapy apparatus comprising: a first ultrasound generating source for irradiating focused ultrasound used in therapeutical purposes; and an intraluminal catheter equipped with a second ultrasound generating source, which is used to be inserted into a region in the vicinity of an irradiation target region of the focused ultrasound; wherein: the ultrasound generated from the first ultrasound generating source is synthesized with ultrasound generated from the second ultrasound generating source so as to produce a standing wave. As a consequence, the generation of the cavitation can be easily controlled, and thus, the medical treatment can be carried out in a proper manner. It should also be noted that the frequency of the ultrasound generated from the second ultrasound generating source may be preferably xe2x80x9c2nxe2x80x9d times higher than, or xe2x80x9c1/2nxe2x80x9d times lower than the frequency of the ultrasound generated from the first ultrasound generating source, (symbol xe2x80x9cnxe2x80x9d is an integer more than, or equal to 1).